Antiarrhythmic · Local anesthetic
Lidocaine
Indications
- Shock-refractory VF or pulseless VT (ACLS alternative to amiodarone)
- Ventricular arrhythmias from ischemia or cardiac surgery, including stable VT
- Infiltration, nerve block, epidural and IV regional (Bier) anesthesia
- Topical airway anesthesia for awake intubation or bronchoscopy
- Blunting the response to laryngoscopy (off-label; weak evidence)
- Perioperative opioid-sparing infusion (off-label)
Dosing
Lidocaine drip card and mL/h converterStart: After a 1–1.5 mg/kg bolus, 1–4 mg/min
| Where | Dose |
|---|---|
| Cardiac arrest | Lidocaine: 1–1.5 mg/kg, then 0.5–0.75 mg/kg every 5–10 min (max 3 mg/kg) |
| Rhythm control | Lidocaine: 1–1.5 mg/kg; then 1–4 mg/min |
| Airway and RSI | Lidocaine (pre-RSI, raised ICP): 1.5 mg/kg 3 min before laryngoscopy; evidence is weak |
On the quick cards
Mechanism of action
Lidocaine blocks voltage-gated Na⁺ channels from inside the cell: the un-ionized base crosses the membrane, re-ionizes, and the cation binds the inner pore (domain IV, S6) of open or inactivated channels, stopping conduction in nerves. As a Vaughan Williams class Ib drug it binds and releases within a beat, so block builds in depolarized ischemic tissue and at fast rates. It shortens Purkinje action potentials and suppresses ventricular automaticity and reentry, sparing the normal QRS, atria and AV node.
Pharmacology
- Cardiovascular: suppresses ischemic ventricular ectopy and reentry; little change in contractility or BP at therapeutic levels (label); no atrial effect
- CNS: low levels sedate and are anticonvulsant; toxic levels block inhibitory neurons first, so excitation and seizures come before CNS depression
- Peripheral nerve: autonomic and pain fibers block before touch and motor fibers
- Respiratory: suppresses cough and airway reflexes
- Other: anti-inflammatory and antihyperalgesic actions underlie its opioid-sparing effect
Pharmacokinetics
| Onset | IV about 1 min |
|---|---|
| Duration | 10–20 min after an IV bolus (redistribution); epinephrine prolongs local blocks |
| Half-life | 1.5–2 h (label); doubled or more in liver disease, longer in heart failure and after 24 h of infusion |
| Distribution | Vd about 1–2 L/kg, smaller in heart failure; crosses the BBB and placenta (label) |
| Protein binding | 60–80%, mainly to α1-acid glycoprotein, which rises after MI and surgery |
| Metabolism | CYP1A2 and CYP3A4 to MEGX (active, adds to toxicity), then GX; high extraction, so clearance follows liver blood flow |
| Elimination | Urine: about 90% as metabolites, under 10% unchanged (label) |
| Adjustments | Halve the infusion after 24 h (label); GX accumulates in kidney failure |
| Therapeutic level | 1.5–5 mcg/mL; CNS toxicity grows above about 6 mcg/mL (label) |
Chemistry
- An amino amide: lipophilic 2,6-dimethylphenyl (xylidine) ring, amide link and hydrophilic tertiary amine; achiral, unlike bupivacaine and ropivacaine
- pKa about 7.9 (PubChem): about 25% un-ionized at pH 7.4, so onset is fast; acidic, infected tissue traps the cation and weakens the block
- Amide link: liver metabolism and very rare true allergy; reactions usually come from methylparaben or sulfite additives
- For arrhythmias: 20 mg/mL syringes and premixed 4 or 8 mg/mL in D5W; never give epinephrine-containing vials IV
Adverse effects and cautions
In the one-pagers
- ACLS Algorithms in BriefCardiac arrest: two tracks: Exam order: shock, CPR, shock, epinephrine, shock, amiodarone or lidocaine. Epinephrine every 3–5 min is about every other 2-minute cycle.
- Pediatric Assessment and EmergenciesCardiac arrest and choking (2025): Antiarrhythmic: Amiodarone 5 mg/kg (max 300 mg; up to 3 doses, repeats max 150 mg) or lidocaine 1 mg/kg
- Chest Tubes and PneumothoraxHemothorax, effusions and pleural infection: Measure pH at once in a blood-gas analyzer: heparin or lidocaine in the syringe lowers it, delay and air raise it. BTS 2023 drains pleural infection with tubes of 14 F or less, flushed with about 30 mL saline every 6–8 hours, plus antibiotics and nutrition. Up to 20% die within a year; the RAPID score (urea, age, purulence, infection source, albumin) st
- Common EMS MedicationsArrest and rhythm drugs: Lidocaine, class Ib: VF/pVT (amiodarone alternative): 1–1.5 mg/kg, then 0.5–0.75 mg/kg: High-grade block without pacer; amide allergy
- Spinal Motion RestrictionAutonomic dysreflexia: Bladder first: trace the catheter for kinks or a full bag, irrigate gently with 10–15 mL of body-temperature saline and replace it if blocked, or catheterize with 2% lidocaine jelly. No Credé.
- Toxidromes and AntidotesCardiotoxic drugs: TCAs, β-blockers, CCBs, digoxin, LAST: Hypertonic sodium bicarbonate works through the sodium load and the alkalemia: AHA 2023 class 1 for TCAs, 2a for other sodium channel blockers (diphenhydramine, flecainide, lamotrigine, venlafaxine). Bolus until the QRS narrows, within AHA's ceilings (pH 7.50–7.55, sodium 150–155). Treat seizures with benzodiazepines, not phenytoin, and nev
Practice ACLS Algorithms in Brief questions free75 exam-style questions with rationales on the topic where Lidocaine comes up most. No account or download needed.
In the algorithms
- Adult Cardiac Arrest
- Arrest After Cardiac Surgery
- VT Storm
- Local Anesthetic Toxicity
- Pediatric Cardiac Arrest (PALS)
Other antiarrhythmic drugs
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Sources
- FDA label: Lidocaine and 5% dextrose injection (2026)
- FDA label: Xylocaine (2024)
- PubChem: lidocaine
- ASRA 2020 LAST checklist
For education and exam preparation only. Follow your institution’s protocols. Typical adult values for study. Follow your local protocols and medical direction.